1. Field of the Invention
The present invention relates to an elastic wave device for components such as a resonator and a band-pass filter and a method for producing an elastic wave device and, more specifically, to an elastic wave device having a structure in which other materials are provided between a lithium niobate film and a supporting substrate and a method for producing such an elastic wave device.
2. Description of the Related Art
Elastic wave devices have been used as resonators and band-pass filters. Japanese Unexamined Patent Application Publication No. 2004-282232 discloses a surface acoustic wave device having a hard dielectric layer, a piezoelectric film, and an IDT electrode stacked on a dielectric substrate in this order. This surface acoustic wave device, in which a hard dielectric layer is disposed between a dielectric substrate and a piezoelectric film, offers an increased acoustic velocity of the surface acoustic wave. This allows the frequency of the surface acoustic wave device to be increased.
The surface acoustic wave device described in Japanese Unexamined Patent Application Publication No. 2004-282232 offers an increased acoustic velocity obtained through the formation of a hard dielectric layer. This means that a high-acoustic-velocity hard dielectric layer is disposed on the bottom of a piezoelectric film. This causes the elastic wave to propagate concentrating in the piezoelectric film. As a result, wave modes other than the surface acoustic wave to be used often occur, including 1) higher-order modes of that surface acoustic wave, 2) an elastic wave that propagates reflecting off of the surface of the piezoelectric film and the boundary between the piezoelectric film and the hard dielectric layer like a plate wave, and 3) higher-order modes of this elastic wave. It has therefore been a disadvantage that large spurious responses appear in addition to the mode of surface acoustic wave to be used.